It's like Mari said; people don't want to admit these things, even when they know it. They'll wriggle around, find whatever excuses they can grab at. Papyrus sighs, disappointed. 'Lazybones' was never really the word for his brother, was it? 'Contrary' is more like it. Whatever cause Papyrus is pushing, somehow there Sans is, opposing him.

"You let me decide before," he points out, and it's not as kindly and gentle. Biting, frustrated. "When you were hurt, and couldn't decide things for yourself... It's the same thing now. I can't stand idly by while... while people suffer."